Composition and distribution characteristics of vegetation in different natural restoration periods in semi-arid loess region
[Background] After decades of returning farmland to forests and grasslands,vegetation in semi-arid loess region has been significantly restored.Investigating the dynamics of plant community during natural restoration process could be helpful in managing the ecosystem and further promoting the restoration rate.[Methods] A hill top of 8.89 hm2 enclosed around 25-32 years was taken as the study area and geostatistical analysis was applied to explore the changes of species composition and structure and spatial heterogeneity of the plant community based on 31 plants quadrats of 1 m × 0.5 m in 2009 and 2016 respectively.[Results] 1) From 2009 to 2016,16 new species were found while the life form was still mainly concentrated in perennial herbaceous plants in whole slope.With the dominated species changed from Artemisia sacrorum,Artemisia leucophylla,Stipa capillata,Lespedeza bicolor and Artemisia frigida to Artemisia sacrorum,Carex tristachya,Cleistogenes chinensis,Lespedeza bicolor and Artemisia frigida.The dominance of subshrub increased significantly.2) The average biomass of the quadrats in 2009 (98.57 g/m2) was significantly different that in 2016 (141.27 g/m2) in the level of 0.01.The differences of biomass on lower slopes and upper slopes became smaller in 2016 indicating that environmental factors had less impact on vegetation growth.3) The species diversity index increased significantly.The average values of Margalef index,Shannon-Wiener index and Pielou index increased from 1.361,1.510 and 0.764 in 2009 to 1.831,1.716 and 0.841 in 2016,indicating that the community became more stable.Compared to other site types with the species diversity increased remarkably,the species diversity index in lower-semi-sunny slope had little change indicating that the community had almost reached a steady state.4) Compared to 2009,spatial autocorrelation of plant coverage,height,biomass and ratio of dry to fresh became weak in 2016.The spatial autocorrelation of Margalef index changed from strong to weak and the autocorrelation distance was about 60 m.Shannon-Wiener index did not show significant spatial autocorrelation both in 2009 and 2016.The spatial autocorrelation of Pielou index changed from positive correlation to negative.It indicates that the spatial variability of plant richness increased while the spatial variability of plant homogeneity decreased.Overall,plant species were richer,the spatial distribution was more uniform and community stability was enhanced on the investigated slope.[Conclusions] From 2009 to 2016,the number of species in the study area increased and the species diversity index showed an increasing trend.The plant life-form of perennial herbaceous plants still dominated in the study area.Results indicated that the community on the hill top became more stable but not reached to a steady state after 32 years of natural restoration and human intervention is necessary to accelerate the natural restoration rate.
国家科技期刊平台
NSTL
万方数据
维普
